Size control for cathode-ray tube deflection circuits



Oct. 27, 1953 R. K. LOCKHART 2,657,332

SIZE CONTROL FOR CATHODE-RAY TUBE DEF'LECTION CIRCUITS 2 Sheets-Sheet 1Filed Jan. 29, 1949 514W 7'00 TH INPUT za M INVENTOR Ebegi .Zacifiari IiORNEY Oct. 27, 1953 R. K. LOCKHART 2,657,332

SIZE CONTROL FOR CATHODE-RAY TUBE DEFLECTION CIRCUITS F iled Jan. 29,1949 2 Sheets-Sheet 2 INVENTOR fikrllilaciilzart Patented Oct. 27, 1953aesrssz SIZE CONTROL FOR CATHODE-RAY TUBE 'DEFLECTI ION CIRCUITS RobertK. Lockhart, Collingswood,iN. J., assignor to Radio Corporation ofAmerica; a corporation f. De war Application.January 29, 1949, Ser ialNo, 73,648

S CIain s (01. 315 -37), v

The present invention relates to. size control systems for cathode ray tbe sweeper deflection circuits and more particularly, but not neces-,sarily exclusively, to novelsize control systems in which there issubstantially no variationof linearity with size change and which areindependent of and do not affect an associated generator of a deflectionwaveform.

It will, therefore, be seen that two important objects of the presentinvention are to provide a size control for a cathode ray tubedeflection system which maintains the desired linear wave? form ofthesweep or deflection voltage or cur'-. rent and which also does notreact in any way upon the generator of the deflection waveform,particularly with-respectfto the frequency of operation of thegenerator.

The system of the present invention in the several embodiments disclosedherein includes a" wave comparison arrangement for automaticallymaintaining a desireduwaveform, and the novel size control of thepresent invention is associated with the wave comparison arrangement ina novel way so that, with a givenlinear'input wave, the amplitude of thewave may be changed while maintaining the desired linear waveform fordeflection. The input wave which is to be reproduced by thewave'comparison'af rangement may remain at substantially constantamplitude, and where it is notinecessary to vary the amplitude oiltheinput wave, it may be obtained with the desired and predetermined degreeof linearity, In known systems when it is necessary to change theamplitude of the input waye, there is an inherent variation of.linearity" with size change which, hile small,.'is still noticeable uponthe screen of a cathode ray tube. If a. blocking oscillator. somewhat'of. the type dis closed in Patent No. 2,101,520, granted December '7,1937, to W. A. Tolsonand Tolson reissue. patent Re. 20,338, datedApril30, 1937, is em? ployed as the source of :the sawtooth waveformultimately tobe used for deflection purposes, the size control will-alsohave an effect. uponfthe blocking oscillatorifrequency or speed whichre} quires a'simultaneousadjustment or synchroni zation'of holdcontrols. With a size control embodying features, of the presentinvention, linearity not noticeably afiected even with closemeasurement. Erequencyor speed is ,not changed sincethe sawtoothformingi'circuit conditions are not changedin any:I'na nner. v

A further object ofzthielinvention is to. provide a system/for derivingland employingfa, differen tial signal which is efieetive inl accordance.with the n ioeor,maint n nath i si e were,- form of 'anuoutput signaland .for changinghthe amplitude of th,e ,outp,ut signal A still furtherobject, of'fthe invention, is to provide a, novel arrangement.forobtaining size control inthe deflection circuits associated with acathode raytube.

Other objectsand advantages .of the invention will, of course.become'apparent and immediately,

suggest themselves to .tIiQSeskiHed inthe art. to which the invention isdirectedjfromareading of the following specificationin connectionwiththe accompanying drawings in which:

Fig. 1 shows, diagrammatically, cathode. ray

beam deflecting apparatus embodying the inven; tion; M

Fig. 2 is a diagrammatic showing of another,

embodiment of the invention; and

Fig. 3 is a diagrammatic showing, of a fur: ther embodiment of .theinvention.

Referring 'for the present to Fig. 1 of the draw? ing, there is shown,byway of example, aI defie'ction circuitifor defleeting'the' cathode raybeam of a cathoderay tube (not shown), along one,

axis, for example, the vertical axis. Another similar deflectioncircuitv (notshown) maybe employed to produce deflection 'along ani axisat right angles .to'the first axis therebyto pro;

duce a scanning. raster ina well-known manner. Arrangements,- generallysimilarto' thatshown herein, by way ofexam'ple, are disclosed .in th'eTolsonpatentaNo. 2,101,520 and No, Re. 20,338, referred to above.

The deflection circuit l selected, by way of errample, e enieeitt n rthe. n se itinvention, althoug h the invention is notliniit'ed in usetocircuitS of this type; comprises a power tube !2, a deflectiontransformer nm, and deflecje The coils I 6' may, be incqrp rjated f tioncoils [6. in a deflection yoke "for use with a cathode ray tube(neither. shown).

A sawtooth wave generator (not shown) of any suitable kind, or typegeneratesjasawtooth wave voltagewhich serveslto: drive ,the j'deflectiori system, shown schematically; by Fig, 1 of the draw; ing. Thevoltagewave supplied from. thefsaw tooth wave source is shown:conventionally is designatedby reference "seawater; is; This wave 19 isapplied, mmug crippling. condenses 23 to the grid, 25 of .thepowerp'tubei'z A portion of the sawtooth wave l0','shown convention:

ally and indicated byfrefere'nce character Z B is applied, through a:resistor 3i to the: resistor v 32 of a potentiometer 335 The resistor, 4

web as e swee en? enem r m; 1.1;.

cuit for the grid 25 of the tube I2. These elements will be referred tohereinafter in detail in connection with the operation of a mixing orcontrol tube plied to the grid 2%; is suitable for the purpose ofdriving a sawtooth of current through the deflection coils It which areconnected to the secondary 38 of the deflection transformer id. In theforegoing the waveform I9 is assumed to be a sawtooth voltage. However,it will be understood that this wave may take other forms depending onthe amount of inductance on the circuit particularly with respect to theplate resistance of the tube I2. Normally, for high frequency deflectiona sawtooth I5 will drive a sawtooth of current through the deflectioncoils i6. Irrespective of the waveform developed for application to thegrid 25, this wave serves as a comparison standard so that thedeflection wave is made to conform therewith while its amplitude isvaried in accordance with the invention.

A comparison wave i i is obtained from the deflection coil I5 which issubstantially a replica of the waveform of the deflection current and,therefore, contains any irregularities or departures of deflectionwaveform from the desired waveform. The waveform ii is applied througha. resistor 43 to the end of the potentiometer 3-3 opposite to theresistor 3|. The resistors 3! and 23 are shunted by condensers l5 and 4%respectively to avoid slow-down of the retrace. They serve to compensatethe balancing network for the higher frequencies of the return trace ina manner by now well known to those skilled in ;he art.

As mentioned above, the returned circuit for the grid 26 is through theresistors 3!, 32, 53 and bhe transformer secondary 38 together with the:leflection coil IS. The cathode 48 of the tube I2 is connected to areference point, such as ground, through a cathode resistor 5i. This re-;istor is shunted by a condenser bz in the usual nanner so that a biasis provided for the grid 26 without an undue amount of cathode degen-:ration.

The anode 5 of the tube !2 is connected in the isual manner through theprimary 58 of the ransformer M to a suitable source (not shown) If platevoltage as indicated schematically at SI.

The anode 63 of the previously mentioned conrol tube 35 is connectedthrough a resistor Gd 0 the anode 54 of the tube I2. The tubes I2 and 6may be considered as being connected in paralel for certain purposes tobe described. The creen grid 66 of the tube 36 is connected throughresistor 63 to the above mentioned source of lositive voltage asindicated at reference charvcter 6 I. By-pass condenser G5! to ground isproided for the screen grid of this tube.

The control grid i2 of the tube 35 is connected 3 the slider M of thepreviously mentioned poentiometer 33 by way of a physical conductor 5.It is to be noted at this point that with the Iider 14 at the electricalmid-point of the reistor 32, if the amplitudes of the waves 28 and Idiffer, the halves of the resistor 32 will have oltage values inverselyproportional to the amlitude of the respective wave. If the waveforms Sand 4! are equal, the potential at the slider i will remainsubstantially fixed and the plate irrent of the tube 36 will remainsubstantially l a steady state condition. If the waveform iownconventionally as indicated by the referice character M changes withrespect to the aveform 28, the potential applied to the grid Thewaveform 89 which is ap- 12 of the tube 36 will shift in a direction tochange the conductivity of the tube 38 in such a way as to correct thisdistortion Size control is obtained in accordance with this invention byshifting the slider H5 along the resistor 32 of the potentiometer 33. Ifthe potentiometer is adjusted so that the sliding contact is movedtoward the resistor M, the circuit is unbalanced toward the source whichprovides the waveform 23 which serves as a standard. In this position ofthe potentiometer slider a component of the sawtooth 28 is present alongwith such differential voltage as may exist at the slider i i, and thegrid 12 experiences the application, not only of the differentialcorrecting voltage, but the rising sawtooth voltage, and the tubes I 2and 36 deliver additional power to the deflection transformer I lwithout impairing the waveform correcting effect of the tube 35. If thepotentiometer slider is adjusted toward the resistor 63 then thesawtooth component, which is added, has the phase of the sawtooth dl.The output of the tube 33 will be degenerated with a resulting reductionin the size of the deflection current or voltage waveform and aresulting reduction in size of extent of the sweep. In a televisionreceiver, there will be a resulting reduction in the size of theproduced image.

Fig. 2 of the drawing discloses an embodiment of the invention employingan amplifier whereby to obtain a larger power output both for wave shapecorrecting and for size control. In this figure the power output tube 8Iwhich serves to drive deflection currents through the yoke 82 is similarto the tube E2 of Fig. 1, and its anode 84 is connected through theprimary B5 of a deflection transformer 8? to a suitable source (notshown) of high positive potential as indicated schematically atreference character 33. The secondary SI of the transformer 87 isconnected through a current conducting path to deflection coils B2. Theconnection to the yoke 82 includes a relatively small resistor 83 acrosswhich a comparison wave 94 is developed. This wave M is a voltage wavewhich is substantially a replica of the waveform of the deflectioncurrent and, therefore, contains any irregularities of departures of thedeflection current wave from the desired waveform 98 which is suppliedto the grid 93 of the tube 8|. One end of the resistor 93 is connectedto ground to provide a ground return for the control circuit and theremaining end is coupled through a connection IGI to the signal grid m3of an amplifier tube I64. The anode 165 of the tube I6 3 is connectedthrough a load resistor I 58 to a source of positive potential (notshown) and indicated schematically at I09. It will be understood bythose skilled in the art that connections I69 and 88 may be joined in asuitable manner. The tube IE4, a tetrode type, for example, may includea screen grid III with suitable positive biasing connections as shown.

The amplified and inverted voltage wave lid is coupled through acoupling condenser H5 to the junction points of resistors H6 and Ill. Itwill be noted that the resistor H6 corresponds to the resistor 53 ofFig. 1. The resistor II I is added in place of the yoke coils of Fig. lof the drawings.

The input wave 95 is applied through a resistor IIS to one terminal ofthe resistor H9 of a potentiometer I2I. The resistors IIS and H8 areshunted by condensers I24 and I26 respectively for the purpose alreadyexplained in connection with Fig. 1 of the drawings.

ThB.;-.t\ihe,..=. I 28: functions in. a..manner similar: to the .tube-.of Fig; 1 of the drawingsyandits Sig-=- nal. grid: I29 ".is coupled by-a. connection: 13 I: :to. 1

The. anode .Iddrof thertube. I28-"is: connected through the 1 sliderE32 1. of .s'the-potentiometere I2 is a resistor I29tto .theanode 84 .ofthe tube-:8]. Fromqthen description. given :above in connectionwith Fig.1 of the drawings, it is believed that the anode of operation. inthe-arrangement of Fig. 2 ofcthe drawings; will be. *understood.

Fig.- 3 discloses va modification: of. the :invention in :whichuthe.comparisonasignal. is. impressed in a novel manner onthe cathode ofthemixer tube;

The cathode; being-in; phase. with. the grid... allows plate icurrent toflow accordlngto; differencesin;

the. respective slopes of the original or standard signal and thecomparisonisignal. under 'condi tions of-balance.

the center of its range;

The-output tube .5 5 t1, thedeiiection transformer i 53,, the yokegcoils .i 5d and: the :resistor I 55iare -as sociated. together in the:same way as thoseof- Fig.

2, for example; The input signal I58, which isthe: original or standard.signal, is coupled. to the grid,:I59 of the tube 15! bya. couplingcondenser I52, The.;.de.fiection waveform. I6 l;is; injected on orsuppliedtothe cathode Ififi'ofna mixertube by way'ofia couplingcondenser I59. The plate I'H of the tubeififi isconnected through aresistor.

nal1l53is supplied through a resistor I19 to'one' end of the resistorI85 ofa-potentiometer- I82.

As stated above, signal grid 84 fthe mixer-tube- !68 are in phase withsignals applied to thecathodeof. this tube. The signal grid I iii-isconnected to the slider I85. Therefore,- the signal Itt andthe signal IM subtract in the-plate current *ofthe mixer tube giving rise to adifferential signal represented by a change in plate current when thereis a dii ference between the waveform I64 and Hit.

A tube I83 receives the difierential signal on its signal grid I39 byway of a coupling condenser &2. A grid resistor is provided for thesignal grid ltd. The plate [96 is connected, for example, to the samesource of high positive potential as is indicated at reference characterI13. ifhe cathode 99 of the tube I83 is connected to the cathode 23! ofthe tube It'll. The tube I88 functions as a cathode follower effectivein parallel with the tube Iti, which functions in the usual manner, andfor conditions of unbalance, the operation of the system, with regard tothe tube I88, is substantially the reverse of that obtained with theembodiments of Figs. 1 and 2 of the drawings. If the potentiometer I82is adjusted toward the resistor I19, the sawtooth component will be suchto drive the grid of this tube slightly more negative.

What is claimed is:

1. A system for maintaining a desired waveform of variable amplitudecomprising an electric wave source, a utilization circuit for said wavecoupled to said source, a wave comparison device, means for applying anelectric wave from said The; balancing.;potentiometer= is again/so.placed'that the balance :point :is near wave source tQ-One :terminal.ofgsaid oomparison.--,

device, =meansfor'applying-awvave from said uti-' lizationvcircuitto asecond terminal-of said comparisondevice in opposite phase relationshipto the-wave appliedzfromsaid .wave source and of substantially the-sameamplitude, said comparison device having; means .including a resistorconnected'between said'two terminals for deriv-.

ing a differential effect, and adjustablemeans for applying saiddifferential effect to said utilization circuitato offset .azdeparturein the waveform appeating-sin said utilization device from the waveform:supplied .bysaid electric wave source. said adjustable means serving tovary .the amplitude of the :waveforrn. appearing in the utilizationdevice;v

2; A system: for. maintain-mg a. desired waveformcornprisingarr-electric wave source, utilizationapparatus operating: under controlof said wave. an electronictub'e having at least a cathode, ananode-and. a control electrode, an anode circuit for said anode,meansfor coupling said anodecircuit to said utilization device, meansfor impressing a. wave from said source between said cathode andicontrol'electrode, a wave comparison device, means for applying anelectric wave:

from'said wavesource to one-terminal of said comparison device, meansforapplying a wave from said'utilizationapparatus to a second terminal ofsaid comparison device in opposite phase relationship to thewave:applied from said wave source. and of substantially the sameamplitude, said comparison devicehaving means for deriving adifierential'effect, and adjustable means including -a resistor'connected betweensaid two terminalsfor applying saiddifferential effect to the anodecircuit of said tube.

3..Arsystem for maintaining adesired waveform comprisingan electricwavesource, a utilization circuit for said-:wave-coupled tosaid source, awave comparison devioe comprising an electronictu'ce, saidtube having atleast a cathode, an anode,.andanelectrodeefiective to control currentflow'throughsaid tubefaresistance in the input circuitiof saidatube,meansforapplying an electric wave-from said wave source to one end ofsaid resistancameans for applying a wave from said utilization circuitto the other end of said resistance in opposite phase relationship tothe wave applied from said wave source, a potentiometer connection tosaid resistance from said electrode, said tube supplying a differentialeffect upon a variation in waveform in said wave applied from saidutilization circuit, and means for applying said differential effect tosaid utilization circuit, whereby said differential effect serves tosupply any necessary amplitude chan e in the waveform applied to saidutilization circuit.

4. In a deflection system for deflecting the cathode ray beam of acathode ray tube having a sawtooth Wave source, a deflection coil, 2.driver tube controlled by a wave from said source for driving a beamdeflecting current through said coil, means for coupling said tube tosaid coil; a wave comparison device connected between said driver tubeand said coil and comprising an electronic tube, a control electrode forsaid tube, means including a resistor for applying an electric wave fromsaid sawtooth Wave generator to said control electrode, a connection tosaid coil including a second resistor for applying 2. voltage Waverepresenting the current wave in said coil to said control electrode inopposite phase relationship to the wave applied from said wavegenerator, a potentiometer between said resistors,

an adjustable connection from said potentiometer to said controlelectrode, said comparison device having means for supplying adifferential effect corresponding to a difference in amplitude betweenthe waveform applied from said source to said driver tube and thewaveform representing the current wave in said coil, and means forapplying said differential effect to the output of said driver tube,

5. A system for maintaining a desired Waveform comprising a firstelectronic tube having a cathode, anode and a control electrode, autilization circuit coupled to said anode, means for supplying asawtooth wave to said control electrode, a second electronic tube havinga cathode, anode and a control electrode, means for supplying a voltageWaveform from said utilization circuit to the cathode of said secondtube, means to supply a sawtooth voltage waveform corresponding to saidfirst named sawtooth wave to the control electrode of said second tube,a third elec tronic tube comprising a cathode, anode and a controlelectrode, said cathode of said third electronic tube being directlyconnected to the oathode of said first electronic tube, means forcoupling the grid of said third electronic tube to the anode of saidsecond electronic tube, and means for maintaining the output of saidthird electronic tube substantially constant in response to equalamplitudes of said input waveform and said waveform from saidutilization circuit.

6. A system for maintaining a desired waveform of variable amplitudecomprising a first electronic tube having a cathode, anode, and acontrol electrode, a utilization circuit coupled to said anode, meansfor supplying a sawtooth wave to said control electrode, a secondelectronic tube having a cathode, anode and a control electrode, meansfor supplying a voltage waveform from said utilization circuit to thecathode of said second tube, means including a potentiometer to supply asawtooth voltage waveform corresponding to said first named sawtoothwave to the control electrode of said second tube, a third electronictube comprising a cathode, anode and a control electrode, said cathodeof said third electronic tube being connected to the cathode of saidfirst electronic tube with substantially no impedance, means forcoupling the grid of said third electronic tube to the anode of saidsecond electronic tube, and means for maintaining the output of saidthird electronic tube substantially constant in response to equalamplitudes for said input waveform and said waveform from saidutilization circuit.

7. A system for maintaining a desired waveform of variable amplitudecomprising a first electronic tube having a cathode, anode and a controlelectrode, a utilization circuit coupled to said anode, means forsupplying a sawtooth wave to said control electrode, a second electronictube having a cathode, anode and a control electrode, means forsupplying a voltage waveform from said utilization circuit to thecathode of said second tube, adjustable means to supply a sawtoothvoltage waveform corresponding to said first named sawtooth Wave fromthe control electrode of the first electronic tube to the controlelectrode of said second tube, a third electronic tube comprising acathode, anode and a control electrode, said cathode of said thirdelectronic tube being connected to the cathode of said first electronictube and having a common cathode resistor, and means for coupling thegrid of said third electronic tube to the anode of said secondelectronic tube.

8. A system as defined in claim 7 including means for maintaining theoutput of said third electronic tube substantially constant in responseto equal amplitudes of said input Waveform and said waveform from saidutilization circuit.

ROBERT K. LOCKHART.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,280,990 White Apr. 28, 1942 2,414,546 Nagel Jan. 21, 19472,423,362 Banker July 1, 1947 2,440,786 Schade May 4, 1948 2,466,537 DeVore Apr. 5, 1949 2,473,208 Larsen June 14, 1949 2,532,534 Bell Dec. 5,1950

